1. Field of the Invention
This invention relates to radiographic imaging, and more particularly to an improved process and apparatus for stimulating information stored on a photo-stimulable phosphor imaging substrate utilizing a non-orthogonal pentaprism.
2. Description of the Prior Art
Traditional x-ray imaging systems using silver-based films are being replaced by radiographic imaging systems using photo-stimulable phosphor imaging substrates or films eliminating the need for physical storage of the resulting imaged film since digital retrieval of the image information includes input and computer storage permitting viewing of such information on a viewer, such as CRT tube assembly. Additionally, such computer stored image information permits facile electronic transmission to any preselect location obviating physical transfer of the thus formed image as developed on the imaging film.
In U.S. Pat. No. 5,874,744 to Goodman, et al., assigned to the same assignee as the present invention herein incorporated by reference, there is disclosed a process and apparatus for processing radiographic information from an anisotropic storage phosphor screen including an opto-electro-mechanical assembly to achieve raster scan of an interrogating beam and including detector and computer assembly.
In U.S. Pat. No. 6,599,004 to Thoms incorporated by reference, there is disclosed a device for reading flexible storage films wherein the flexible storage film having image-wise projected information is positioned on a cylindrically-shaped surface and is caused to be linearly moved there over while being interrogated or scanned via a slot by a light beam generated in a helical line in a continuous manner from a point disposed at the axis of the cylindrically-shaped surface.
In copending application Ser. No. 60/725,984, assigned to the same assignee as the present invention, hereby incorporated by reference, there is disclosed a process and apparatus for interrogating or scanning a photo-stimulable phosphor substrate containing projected image-wise information wherein a laser beam is directed towards a lens to produce a planar light beam directed onto the storage substrate as a focused light line to stimulate luminescent information detected by a linear sensor for collection and transmission to a computer assembly.
If the output signal of the photomultiplier is recorded together with the output signals of the position encoders one obtains an electric image of the x-ray image previously formed in the storage film in the form of exited metastable color centers of the phosphor particles. This image is then further processed electrically in view of changing the scale of reproduction, emphasizing details, improving the signal/noise ratio, etc. The resulting x-ray image may be put into an archive in its original and/or digitally processed form requiring only little space.
The light source or laser beam utilized for the interrogation of the storage film is generated and directed into an orthogonal pentaprism. In the orthogonal pentaprism, the light source or laser beam enters an inlet facet and undergoes two reflections within the pentaprism exiting the outlet facet 90 degrees disposed to the inlet facet and thence to the surface of the storage film. The light source or laser beam is coupled with a sensor diode so as to maintain the light source or laser beam at an appropriate intensity to excite and therefore interrogate and read the surface of the storage film.
The excitation of the surface of the storage film by a laser beam or light source through an orthogonal pentaprism perpendicular to the surface of the storage film often results in a reflection of luminescent light traveling in the reverse direction of the laser or light source and this reflected light being sensed by the sensor diode coupled to the laser or light source causes the level of the light source or laser to vary in intensity, thus contributing to interference-like phenomena which causes the image on the storage film which is being interrogated, captured by the detection unit and photomultiplier and stored to be less than the desirable clarity as a result of the fluctuation in light source or laser intensity. Such reflected light may also be re-reflected onto the storage film thereby resulting in small amounts of additional excitation from the storage film area illuminated by said re-reflected laser light and may therefore be detected by the detecting unit further decreasing the clarity of the image read and stored.
As used herein, the term “storage substrate” is a film plate or sheet including a photo-stimulable phosphor layer is capable of being imaged with ionizing radiation or x-rays which after imaging may be interrogated or scanned with a source of light energy to produce photostimulated luminescence information capable of being digit recovered and stored.